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/*-------------------------------------------------------------------------
*
* blscan.c
* Bloom index scan functions.
*
* Copyright (c) 2016-2021, PostgreSQL Global Development Group
*
* IDENTIFICATION
* contrib/bloom/blscan.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "access/relscan.h"
#include "bloom.h"
#include "miscadmin.h"
#include "pgstat.h"
#include "storage/bufmgr.h"
#include "storage/lmgr.h"
#include "utils/memutils.h"
#include "utils/rel.h"
/*
* Begin scan of bloom index.
*/
IndexScanDesc
blbeginscan(Relation r, int nkeys, int norderbys)
{
IndexScanDesc scan;
BloomScanOpaque so;
scan = RelationGetIndexScan(r, nkeys, norderbys);
so = (BloomScanOpaque) palloc(sizeof(BloomScanOpaqueData));
initBloomState(&so->state, scan->indexRelation);
so->sign = NULL;
scan->opaque = so;
return scan;
}
/*
* Rescan a bloom index.
*/
void
blrescan(IndexScanDesc scan, ScanKey scankey, int nscankeys,
ScanKey orderbys, int norderbys)
{
BloomScanOpaque so = (BloomScanOpaque) scan->opaque;
if (so->sign)
pfree(so->sign);
so->sign = NULL;
if (scankey && scan->numberOfKeys > 0)
{
memmove(scan->keyData, scankey,
scan->numberOfKeys * sizeof(ScanKeyData));
}
}
/*
* End scan of bloom index.
*/
void
blendscan(IndexScanDesc scan)
{
BloomScanOpaque so = (BloomScanOpaque) scan->opaque;
if (so->sign)
pfree(so->sign);
so->sign = NULL;
}
/*
* Insert all matching tuples into a bitmap.
*/
int64
blgetbitmap(IndexScanDesc scan, TIDBitmap *tbm)
{
int64 ntids = 0;
BlockNumber blkno = BLOOM_HEAD_BLKNO,
npages;
int i;
BufferAccessStrategy bas;
BloomScanOpaque so = (BloomScanOpaque) scan->opaque;
if (so->sign == NULL)
{
/* New search: have to calculate search signature */
ScanKey skey = scan->keyData;
so->sign = palloc0(sizeof(BloomSignatureWord) * so->state.opts.bloomLength);
for (i = 0; i < scan->numberOfKeys; i++)
{
/*
* Assume bloom-indexable operators to be strict, so nothing could
* be found for NULL key.
*/
if (skey->sk_flags & SK_ISNULL)
{
pfree(so->sign);
so->sign = NULL;
return 0;
}
/* Add next value to the signature */
signValue(&so->state, so->sign, skey->sk_argument,
skey->sk_attno - 1);
skey++;
}
}
/*
* We're going to read the whole index. This is why we use appropriate
* buffer access strategy.
*/
bas = GetAccessStrategy(BAS_BULKREAD);
npages = RelationGetNumberOfBlocks(scan->indexRelation);
for (blkno = BLOOM_HEAD_BLKNO; blkno < npages; blkno++)
{
Buffer buffer;
Page page;
buffer = ReadBufferExtended(scan->indexRelation, MAIN_FORKNUM,
blkno, RBM_NORMAL, bas);
LockBuffer(buffer, BUFFER_LOCK_SHARE);
page = BufferGetPage(buffer);
TestForOldSnapshot(scan->xs_snapshot, scan->indexRelation, page);
if (!PageIsNew(page) && !BloomPageIsDeleted(page))
{
OffsetNumber offset,
maxOffset = BloomPageGetMaxOffset(page);
for (offset = 1; offset <= maxOffset; offset++)
{
BloomTuple *itup = BloomPageGetTuple(&so->state, page, offset);
bool res = true;
/* Check index signature with scan signature */
for (i = 0; i < so->state.opts.bloomLength; i++)
{
if ((itup->sign[i] & so->sign[i]) != so->sign[i])
{
res = false;
break;
}
}
/* Add matching tuples to bitmap */
if (res)
{
tbm_add_tuples(tbm, &itup->heapPtr, 1, true);
ntids++;
}
}
}
UnlockReleaseBuffer(buffer);
CHECK_FOR_INTERRUPTS();
}
FreeAccessStrategy(bas);
return ntids;
}
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